The NG2 proteoglycan is expressed on the surface of glial precursor cells that are capable of differentiating into either oligodendrocytes or type 2 astrocytes, depending on their environment. Since NG2 may be involved in the development of these precursor cells or in their choice of lineage pathways, it is important to understand the structure, function, and control of expression of the molecule. Structural information will be obtained through the use of a panel of antibodies directed against different domains of the NG2 peptide. Immunochemical mapping of the spatial relationship of these domains will be accomplished through the use of defined fragments of the NG2 molecule and through the use of electron microscopy to examine rotary shadowed preparations of NG2. Acquisition of structural information will be accelerated by isolation and sequencing of cDNA clones for NG2. Such clones will also provide probes for the study of NG2 mRNA expression in developing systems. Possible adhesive interactions of NG2 with extracellular matrix components will be studied using NG2- containing liposomes or NG2-coated beads. Toward this same end, immunoelectron microscopy will be used to look for co-distribution of NG2 and various matrix components in the matrix formed by the R14 retinal cell line. Finally, cultures of optic nerve and cerebellum will be used to investigate the possibility that NG2 influences the choice of lineage pathway taken by glial precursors. Cultures treated with antibody against NG2 will be examined for evidence of alterations in the normal distribution of differentiated glial derivatives.